Pick-up for phonographs



April 14, 1959 H. DA cosTA PICK-UP FOR PHONOGRAPHS Fild Sept. 10, 1954 United States Patent PICK-UP FOR PHONOGRAPHS Harry da Costa, Snaresbroolr, London, England, assignor to The Plessey Company Limited, Ilford, England, a British company Application September 10, 1954, Serial No. 455,212

Claims priority, application Great Britain September 17, 1953 1 Claim. (Cl. 274-23) This invention relates to a spring support for a pick-up for phonographs.

It has previously been proposed to provide a spring support for a pick-up arm with an adjusting means for varying the pressure of the needle or stylus upon a record.

An object of the present invention is to provide an improved construction which is simple to set for obtaining a desired reduction of the pressure of the needle or stylus upon the record and inexpensive to manufacture.

According to the present invention the tension device consists of a helical spring which is threaded over a rod in two parts with relative rotation and one end of the spring frictionally gripping one part of the rod and the other end extending tangentially. Said rod is mounted transversely in the hinged element and the free end of the spring bears against the underside of the pick-up or hinged element so that when the rod is rotated in one direction after releasing the clamping means, the coils of the spring are wound to impart the desired tension, and in a reverse direction to reduce the tension and finally tightening up the clamp means.

The invention will now be described with reference to the accompanying drawing in which- Fig. 1 is a fragmentary plan view of a phonograph.

Fig. 2 is an enlarged view in section on the line 2--2 of Fig. 1, and

Fig. 3 is an underneath plan of the pick-up arm.

Referring to the drawing- A pick-up arm 1 has a rod divided into two parts or rod members 2, 3. The part 2 is partly of larger diameter for the purpose hereinafter set forth. The two parts 2, 3 of the rods are inserted through aligned holes 4 in the respective side walls of a U-shaped hinged bracket 5.

A helical spring 6 is threaded over the larger diameter of the part 2 and over the rod 3 and the inner end of the part 3 is located in a running fit in a bore 7 in the larger diameter of the part 2. The end 8 of the helical spring 6 abuts against a flange 9 integral with the part 2 and said spring 6 frictionally grips the part of larger diameter, while the other end 10 of the spring 6 is extended tangentially and abuts against the base of the U-shaped bracket 5.

A vertical spindle 11 fixed to the U-shaped bracket 5 is rotatably mounted in a pillar fixed to the base plate 15 for supporting the pick-up arm 1.

The outer end of the part 2 of the rod has a screw- 2 driver slot 12, and both parts extend in opposite directions across the undersides of the pick-up arm 1, as indicated in Fig. 2.

The clamping means for holding the rod against rotation consists of two screws, 13, 13, having a clamp plate or washer 14 thereon, which are screwed into the underside of the pick-up arm 1, adjacent the outer ends of the rod 2 and 3, whereby the clamp plates 14 hold the rod against rotation.

To adjust the tension of the spring 6, it is only necessary to slacken off the screw 13, then rotate the rod with the aid of a screw-driver to vary the tension of the spring 6 and finally tighten up the screw 13, whereby the pressure of the stylus on a phonograph record can be adjusted.

I claim:

A phonograph pick-up arm assembly comprising an arm-support bracket having two parallel upstanding walls, a pick-up arm having a part of inverted 'U-section adapted to accommodate at least part of said parallel walls, said parallel walls having aligned bores for pivotal attachment of said arm, and said U-section part having two recesses one at each side, aligned with said bores in the parallel bracket walls, a first pin member located in one of said recesses to extend through the hole in the adjacent bracket wall and project towards the other wall across the greater part of the width of said bracket, a second pin member located in the other recess and extending inwardly through the hole in the other bracket wall and including a socket portion having a greater diameter than the first pin member, said socket portion extending from said last-mentioned bracket wall towards the first-mentioned bracket wall over part of the width of the bracket and accommodating and rotatably supporting the projecting end of the first pin member, the outer end of the second pin member being provided with a screw driver slot, and the recess accommodating said outer end extending through the outer surface of the pick-up arm, a helical torsion spring arranged round both said pin members between said parallel walls and having one end extended tangentially and supported on said bracket against rotation about the axis of said pin, the other end of the spring being attached to said socket portion for common rotation therewith, and clamping screws each having a shoulder overlapping one of said pin members in its recess for retaining each pin member in its recess and clamping it against rotation, the pick-up arm being provided with screw-threaded bores for engagement by the threads of said screws.

References Cited in the file of this patent UNITED STATES PATENTS 1,453,613 Wolfi May 1, 1923 1,983,078 Grubman Dec. 4, 1934 2,271,039 Slade et al. Jan. 27, 1942 2,600,914 Palo et al June 17, 1952 2,645,498 Miller et al July 14, 1953 FOREIGN PATENTS 3,704/31 Australia Aug. 25, 1932 

